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<a name="C_002b_002b-Extensions"></a>
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<p>
Next: <a href="Objective_002dC.html#Objective_002dC" accesskey="n" rel="next">Objective-C</a>, Previous: <a href="C-Extensions.html#C-Extensions" accesskey="p" rel="prev">C Extensions</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p>
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<a name="Extensions-to-the-C_002b_002b-Language"></a>
<h2 class="chapter">7 Extensions to the C++ Language</h2>
<a name="index-extensions_002c-C_002b_002b-language"></a>
<a name="index-C_002b_002b-language-extensions"></a>

<p>The GNU compiler provides these extensions to the C++ language (and you
can also use most of the C language extensions in your C++ programs).  If you
want to write code that checks whether these features are available, you can
test for the GNU compiler the same way as for C programs: check for a
predefined macro <code>__GNUC__</code>.  You can also use <code>__GNUG__</code> to
test specifically for GNU C++ (see <a href="http://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html#Common-Predefined-Macros">Predefined Macros</a> in <cite>The GNU C Preprocessor</cite>).
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<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="C_002b_002b-Volatiles.html#C_002b_002b-Volatiles" accesskey="1">C++ Volatiles</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">What constitutes an access to a volatile object.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Restricted-Pointers.html#Restricted-Pointers" accesskey="2">Restricted Pointers</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">C99 restricted pointers and references.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Vague-Linkage.html#Vague-Linkage" accesskey="3">Vague Linkage</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Where G++ puts inlines, vtables and such.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="C_002b_002b-Interface.html#C_002b_002b-Interface" accesskey="4">C++ Interface</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">You can use a single C++ header file for both
                        declarations and definitions.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Template-Instantiation.html#Template-Instantiation" accesskey="5">Template Instantiation</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Methods for ensuring that exactly one copy of
                        each needed template instantiation is emitted.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Bound-member-functions.html#Bound-member-functions" accesskey="6">Bound member functions</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">You can extract a function pointer to the
                        method denoted by a &lsquo;<samp>-&gt;*</samp>&rsquo; or &lsquo;<samp>.*</samp>&rsquo; expression.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="C_002b_002b-Attributes.html#C_002b_002b-Attributes" accesskey="7">C++ Attributes</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Variable, function, and type attributes for C++ only.
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<tr><td align="left" valign="top">&bull; <a href="Function-Multiversioning.html#Function-Multiversioning" accesskey="8">Function Multiversioning</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Declaring multiple function versions.
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<tr><td align="left" valign="top">&bull; <a href="Type-Traits.html#Type-Traits" accesskey="9">Type Traits</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Compiler support for type traits.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="C_002b_002b-Concepts.html#C_002b_002b-Concepts">C++ Concepts</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Improved support for generic programming.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Deprecated-Features.html#Deprecated-Features">Deprecated Features</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Things will disappear from G++.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Backwards-Compatibility.html#Backwards-Compatibility">Backwards Compatibility</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Compatibilities with earlier definitions of C++.
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